I have sonar x3 producer and dimension pro 32 bit installed but when i try to install the expansion it says error cannot find dimension pro 1.5 install. It is installed and works fine. so not sure what to do now.

Sounds like a job for Product Support.
 
http://www.cakewalk.com/Support/Contact
 

I had this with I think the EMU Proteus pack, or maybe Galbanum Piscis that I had purchased ages back. I sorted it out somehow, can't quite remember though, so not much help to you except to say you'll get there, let us know how you get on so if anyone else runs into this problem they will know what to do

See this LINK it may be of assistance. 

Make sure you are installing the appropriate upgrade, for the bit-depth you have installed, so if you had 32-bit installed, you would want the 32-bit upgrade, and 64-bit upgrade for 64-bit installed prior version.
 
Hope that makes sense AND helps, 
 
Bob Bone